This Standard specifies the signalling protocol for the support
of the Transit Counter additional network feature (ANF-TC) at
the Q reference point between Private Integrated Services Network
Exchanges (PINXs) connected together within a Private Integrated
Services Network (PISN).

ANF-TC is a feature that limits the number of Transit PINXs that
a call setup request may be routed through e.g., to protect the
network against indefinite looping.

Service specifications are produced in three stages and according
to the method specified in ETS 300 387. This Standard contains
the stage 3 specification for the Q reference point and satisfies
the requirements identified by the stage 1 and stage 2 specifications
in ECMA-224.

The signalling protocol for ANF-TC operates in association with
the signalling protocols for basic circuit switched call control
(as specified in ECMA-143) and call
independent (connection oriented) signalling connections (as specified
in ECMA-165).

This Standard also specifies additional signalling protocol requirements
for the support of interactions at the Q reference point between
ANF-TC and other supplementary services and ANFs.

This Standard is applicable to PINXs that can interconnect to
form a PISN.

The protocol defined in this Standard forms part of the PSS1
protocol (informally known as QSIG).